1. Field of the Invention
The invention relates to guardrail extruder devices used with guardrail installations. In particular aspects, the invention relates to the design of impact head assemblies for such devices.
2. Description of the Related Art
Guardrail extruder terminals are a popular and effective end treatment for guardrail installations. During an end-on impact to a guardrail end, a guardrail extruder terminal will flatten and bend a corrugated rail member and extrude the flattened portion away from the roadway. Terminals of this type are described in U.S. Pat. Nos. 5,078,366 and 4,928,928.
The present invention provides an improved head assembly for a guardrail extruder terminal device. An exemplary head assembly is described that is lighter and more effective than prior art head assemblies. The exemplary head assembly provides a throat that receives a corrugated guardrail. In preferred embodiments, the throat is a squeezing throat that is narrower at the upstream end than at the downstream end. The squeezing throat compresses a rail and flattens it. A curved plate contacts the rail and extrudes it away from the head assembly. The throat is constructed from a pair of side members. In a first described embodiment, the first side member is an elongated, S-shaped plate while the second side member is a short curved plate. Alternative head constructions are described wherein the throat is constructed from side members that are formed of flat plates rather than curved plates. The flat plates may be tapered such that the upstream end of the throat is narrower than the downstream end. Alternatively, the flat plates may be non-tapered wherein the squeezing is accomplished through combined action of the throat and curved deflector plate.
The impact plate of the head assembly is vertically elongated and presents upper and lower overhangs that assist with vehicle engagement. In addition, the impact plate is provided with flanges on either side to help stiffen the plate. The head is also asymmetrical and streamlined. When the impact head is mounted on a rail member, the central point of impact is off-center with respect to the axis of the head.